Background: The prevalence of asthma is relatively low in the Chinese population. There is consistent evidence that growing up on a farm is associated with protection against the subsequent development of asthma.
Objective: To compare the prevalence of asthma in schoolchildren from urban and rural China and to assess the possible protection associated with agricultural and livestock farming.
Methods: Random samples of schoolchildren aged 13-14 years from urban Beijing and rural area around Beijing were studied using the International Study of Asthma and Allergies in Childhood (ISAAC) Phase III protocol. Subjects were studied by questionnaires (n = 7,077) and skin-prick tests (n = 2,126).
Results: The prevalence rates of wheeze in the past year and physicians' diagnosis of asthma were 1.0% and 1.1% in the rural area, and these were significantly lower than 7.2% and 6.3% found in the urban children (P < 0.0001). For the video questionnaire, only 0.3% of rural children reported wheeze in the past year compared with 3.1% in urban children (P < 0.0001). Atopy was 3.22 times higher in urban children compared with rural children (P < 0.0001). For rural schoolchildren, 1,453 (41%) have always been living on agricultural farms since birth and the prevalence rates of their asthma symptoms and atopic sensitization were not significantly different from those who have exposed to livestock farming.
Conclusion: Using the same validated ISAAC questionnaire and objective skin-prick tests, the prevalence rates of asthma and atopic sensitization in rural Chinese children were significantly lower than urban children. Exposure to agricultural farming conferred the same protection as livestock farming.